When Kevin Rosenberg left the Navy in 2003, his professional path seemed clear: He returned to Cardozo Law School to complete the degree he had started pre-9/11, passed the bar in New York and New Jersey and went on to land a job as an attorney.

But two months into his time at a city law firm, Rosenberg, 38, says he was “miserable.”

“I realized, I don’t want to have an office job the rest of my life,” says the Brooklyn native. “I wanted to do my own thing.”

Part of Rosenberg’s malaise was related to the monotony of a desk job. After a long Naval career that included flying jets, hunting submarines in the Persian Gulf and serving with a gunboat/coastal warfare unit in support of Operation Iraqi Freedom, he sorely missed the challenges and teamwork of his active duty days.

He also already had an idea for a start-up that would provide the entrepreneurial challenge he craved: a full-service outfitter that rented, sold, and repaired outdoor gear, as well as offering guided trips.

“I felt like the outdoor community wasn’t being served properly,” says Rosenberg, an adventure buff ever since Ranger training as an ROTC cadet. “And I knew I could a get my own company started pretty much on the cheap.”

So Rosenberg took a small loan from a Navy friend, and set to work starting a Web site that sold and rented outdoor gear and offered citywide delivery. The site went live in March 2009.

“The military definitely gave me the confidence to have a goal and go towards it,” he says of his head-on approach. “You learn that as long as you work hard and think things through, you can do whatever you want.”

But the early venture, which operated entirely from his apartment, had only modest success, and Rosenberg knew he needed a real neighborhood presence to catapult his business off the ground.

So, with scant capital to put towards retail space — and no luck in securing a loan via the vet-friendly Patriot Express loan program — Rosenberg decided to take advantage of a state benefit that grants honorably-discharged veterans the near-exclusive right to vend on the street.

“I ended up making $500 of revenue in the first couple hours,” Rosenberg says of his initial experiment hawking his wares on a Park Slope street, “and I did even better the next day.”

Encouraged, he decided to design a “high-end street stand” complete with solar panels and outdoor lights, and ended up earning a local following within months.

The experience wasn’t without challenges: extreme temperatures, shopkeepers who didn’t want him outside their stores and “near-physical altercations with other street vendors” required Rosenberg to exercise a Navy-trained resolve.

“There were so many times when I could have given up,” says Rosenberg. “What kept me going was that I believed in my idea.”

But his persistence paid off. After a year and half as a street vendor, Rosenberg had made enough money to open a storefront off Seventh Avenue, and Gear to Go Outfitters officially opened its doors last April.

“Having a shop now is huge,” says Rosenberg, who reports healthy business for both equipment sales and rentals, as well as a steady clientele for the wilderness tours he and his fellow guides lead. “I’m proud of what we’ve been able to accomplish.”

These days, he already has his eyes on a larger store space — and he says he one day hopes to replace behemoth outfitters like REI and EMS.

“It’s just about determination,” Rosenberg says of his success so far.

“It’s just doing whatever you have to do to get it done, and I think that comes from the military.”